Experimental study of the effect of nitrogen on titanium-arc cathode erosion

Experimental data on the dependence of titanium erosion rate on cathode temperature, Ar, and N₂ pressure from vacuum to 1 torr and arc motion are presented. Erosion rate is found to decrease with conditions that promote cathode poisoning/contamination. Higher cathode temperatures result in enhanced nitriding (poisoning), leading to a reduced erosion rate. A critical nitrogen pressure (0.001 torr) exists where a sharp drop in erosion is measured. Steered arcs show lower erosion rate values of 38 and 15 μg/C for argon and nitrogen, when compared to random arc values of 45 and 35 μg/C. Erosion rate studies on TiN-coated cathodes show a low value of around 22 μg/C